GETGROUPS

getgroups, setgroups ? get/set list of supplementary group IDs

#include <unistd.h>

int getgroups(int size, gid_t list[]);

#define __USE_BSD
#include <grp.h>

int setgroups(size_t size, const gid_t *list);

getgroups

Up to size supplementary groups are returned in list. If size is zero, list is not modified, but the total number of supplementary groups for the process is returned.

setgroups

Sets the supplementary groups for the process. Only the super-user may use this function.

getgroups

On success, the number of supplementary group IDs is returned. On error, ?1 is returned, and errno is set appropriately.

setgroups

On success, zero is returned. On error, ?1 is returned, and errno is set appropriately.

EFAULT

list has an invalid address.

EPERM

For setgroups, the user is not the super-user.

EINVAL

For setgroups, size is greater than NGROUPS (32 for Linux 2.0.32). For getgroups, size is less than the number of supplementary group IDs, but is not zero.

SVr4, SVID (issue 4 only; these calls were not present in SVr3), X/OPEN, 4.3BSD. The getgroups function is in POSIX.1. Since setgroups requires privilege, it is not covered by POSIX.1.

The __USE_BSD flag probably shouldn’t be required for setgroups.

initgroups(3), getgid(2), setgid(2)